There are numerous types of food preparation processes for preparing food items for further processing or consumption. Many of these require heat transfer to or from a food item. Typically, this heat transfer is manually controlled or pneumatically controlled with a simple PLC (programmed logic controller) system. As a result, the quality and yield of the food item that is being prepared is adversely affected.
For example, a precooking process is used to precook tuna fish for canning the loins (i.e., the desired meat) of the tuna fish. In this precooking process, tuna fish is precooked in live steam. This is done until a target backbone loin temperature is reached at the widest portion of the loins near the backbone of the tuna fish. The loins are then extracted and cleaned. This is done manually by removing the head, tail, and fins of the tuna fish, scraping off the skin and red meat from around the loins, and deboning the loins. The cleaned loins are then ready for packing into a can.
This precooking process is one of the most critical steps for canning tuna fish. It directly affects the yield and the quality of the canned tuna fish. However, as alluded to earlier, a typical precooking process is controlled either manually or pneumatically. The precooking is usually done at a high and constant temperature to enable extraction and cleaning of the loins of the tuna fish. Moreover, manual measurements of the backbone loin temperature at the widest portion of the tuna fish are made in order to determine if the target backbone loin temperature there has been reached. As a result, the surface and the thinner portions of the tuna fish are usually overcooked. This causes yield loss and makes the skinning process very tedious and difficult. In addition, overcooking often causes the skin of the tuna fish to break. This oxidizes the loins and diminishes their quality.
It is evident from the foregoing that precise control of heat transfer in a food preparation process, such as a tuna fish precooking process, is economically important for a food producer. Therefore, it is highly desirable to provide a technique for precise on-line control of the heat transfer in such a process to improve the yield and the quality of the food item being prepared.